Process for tanning leathers and skins



UNITED STATES PATENT OFFICE.

HENRI MORIN, 0E ST.I)ENIS, FRANCE, AssrGNoR TO LA socIETE GENTY, nouen &CIE. (socIETE EN NoM COLLIECTIF ET EN COMMANDI'IE SIMPLE), or PARIS,

FRANCE.

PROCESS FOR TANNING LEATHERS AND SKINS.

No Drawing.

Patented Jan. 24, 1922.

Serial No. 135,368.

(GRANTED UNDER THE PROVISIONS OF THE ACT OF MARCH 3, 1921, 41 STAT. L,1313.)

To all whom. it may concern.

Be it known that I, HENRI MORIN, a citizen of the Republic of France,residing at St.-Denis, Seine Department, 14 Rue Catnlienne, in theRepublic of France, have in-- rented a certain new and useful Processfor Tanning Leathers and Skins, (for which I have obtained French PatentNo. 479,908, filed Oct. 22, 1914, delivr date Feb. 29, 1916,) of whichthe following is a specification.

This invention relates to a process for white tanning leathers andskins. The process consists in the incorporation with the cells of theskins, whatever may be their origin and their nature, of silica or oxideof silicon which, combining with the con stituent elements of the skin,forms with them an insoluble imputrescible composition.

This insoluble composition is above all formed in the layers of thefibres of the skin and prevents them from adhering together. whichallows them to slide upon one another, and thus gives the skin verygreat suppleness.

In order to incorporate the silica into the skin, and to compel it to becombined with the elements which constitute the latter, any substancecontaining silica, in a state of combination, can be employed, but it ispreferable to use either silicate of soda or silicate of potash. andafterward a substance. such as an acid or metallic salt for instance,capable of being combined with the soda or the potash of said silicatein such a way is to liberate silica and to allow its combination withthe organic matter. Nevertheless, the use of a silicate is notabsolutely necessary because the tanning can also be oh tained bydipping the skin in a bath containing gelatinous silica in suspension ordissolution. In a word, the tanning results from the direct combinationof the silica with the skin.

For tanning skins or leathers according to this process the followingmethod of operation may be adopted 1-Tl16 skins coming from a steepingvat, that is to say, when shaved and after having been well rinsed, areimmersed in a bath of water containing per cent to 10 per cent,according to the firmness or suppleness which it is desired to obtain,of silicate of soda or of potash. These silicates should be of theconcentrat on usual in commerce and it will be sufficient, for a skin of800 grammes to 1 kg, to take 3 litres of one of the solutions abovementioned, particularly if operating in a vat or the like, to obtain aperfect tanning. The duration of the immersion and the concentration ofthe solutions of the silicates should. be according to the nature of theskins. their thickness, their out, etc., it is for the operator to fixthese elements by re peated trials. Take as an example the impregnationof a dozen sheep skins of any origin and of medium out. In operating ina vat, 36 litres of solution of silicate at 2?; per cent will besufiicient and the impregnation should not last more than 48 hours. Itis understood that when dealing with skins which are thick or of a veryfirm nature, very close as in the case of leather, the tanning periodwill be rather longer and the quantity of silicate somewhat larger. Ifsplit skins, grain or flesh, are to be treated instead of whole skins,the duration of impregnation will be shorter and the strength of thesilicate solution lower. Indeed all skins and hides designed for alluses can be tanned by the present process.

After having, as above stated, immersed the skins in a solutioncontaining silica and left them therein for several hours, they will beseen to swell considerably. It will then only be necessary to provide asuitable means for separatingthe silica from its combinations and topermit it to be combined with the fibres of the skin, This combinationshould take place relatively slowly. 1t can be effected by means of anysubstances capable of displacing the silica from its combinationswithout injury to the skin such as most mineral or organic acids and alarge number of metallic salts, for example, chloride of zinc, etc.Amongst the substances capable of being used for this action acetic acidgives excellent results, and, up to the present, appears preferable.

The quantity of acid employed should be strictly proportioned to thequantity of silicate contained in the solution; for example, if 100litres of water be employed charged with 5 per cent of silicate, whichrepresents 108 5 kg. of this product, it would be necessary I to add 5kg. of acetic acid at 7 Baum.

porosity of the skins.

This acid can be added all at once or progressively, as'the operator maychoose, and

that without removing the skins from the vat.

hen the acid has been added the combination of. the silica will commenceto take place into the cells of the skin, and in order that the tanningmay be complete it will be necessary to leave the skins for several daysaccording to the thickness and degree of If sheep skins, for example,are to be treated it will only be necessary to allow the action of theacid bath to last for a few days.

Moreover, during the tanning, samples should be taken which should berapidly stove-dried and the edge examined after having cut thematseveral places. If, on the cut edges, a brown streak is perceived theskin is not thoroughly tanned, and it will be necessary to continue thetanning until this streak disappears, that is to say, the tanning willbe completed when the white colour of the skin shall have spreaduniformly to the interior starting from the outer part of the flesh sideto the outer part of the grain side.

lVhen once the tanning is finished the skins are suitably rinsed so asto free them from any trace of non-combined materials without lettingthem dry but allowing them to thoroughly drain.

They are then impregnated with a suitable nutriment or improver untilthe desired degree of suppleness is attained. The question of thenutriment is not here dealt with as the special object of this inventionis the tanning. Moreover nutriments are very numerous and can easily bechosen. That which seems preferable is the nutriment usually employedfor chrome tanning and composed of soap, oil and yolk of eggs; the

recipe can be found in any treatise on tan- 11 tanned skins are not tobe treated with nutriment at once, and they are to be kept white eitherfor subsequent dyeing or to reserve them for a. mixed tanning, they can,after having been rinsed, be impregnated with brine and left to dry inthe air. This method of procedure will allow of keeping the skins withall their supploness as long as may be desired.

Instead of brine a slightly glycerinat'ed water can'be employed. Brineis, however,

preferable to glycerine as a slight excess of the latter substance hasthe effect of attracting the moisture of'the air which tends to producemouldiness upon the skins when they are a-llowed to remain a long timebefore being used.

lVhen it is required to make use of the skins thus prepared it is onlynecessary to rinse them and feed them if it is required to sell them aswhite skins or to dye them and feed them after the dyeing, or, again tofeed them whilst dyeing them, if the nutriment agrees with the dyeing,or, again a mixed tanning may be resorted to, according to therequirements of the work to which the skins are to be subjected, oraccording to the will of the operator.

It is to be observed that this tanning properly carried out is suitablefor all the working requirements of the skin; it compares favourablywith chrome tanning as regards suppleness and firmness of the grain andflesh; itcosts less, requires'less dressings and.

combinations of mixed tanning of vegetable or mineral nature whateverthey may be and is thus suitable for all manufacture, whilst effectingan important economy in the materials employed especially when thesematerials are expensive like for example, sumach employed in moroccoleather dressing.

In any case these mixed tannings are only referred to as examples, theobject of the present invention consisting essentially in the process oftanning according to which silica is incorporated by a suitable meanswith the constituent elements of the skins of animals.

'l'laving now particularly described and ascertained the nature of mysaid invention and in what manner the same is to be performed, I declarethat what I claim is:

'l. process oftanning skins wherein the skin is steepedin an alkalinesilicate solution and'afterwards treated by a solution of acetic acid.

2. A process oftanni'ng skins wherein the skin is steeped in an alkalinesilicate solution, afterwards treated by a silicate decomposing agentand then impregnated with brine and rinsed and, dried.

In testimony, that I claim the foregoing The leather treated is supple,if.

